Switching power converters are used in a wide variety of applications to convert an unregulated power source into various regulated voltage levels by using several switches. For example, a switching DC/DC power converter is used to convert DC power at one voltage level into other regulated DC voltage levels. Such a switching DC/DC power converter usually has a rectifier circuit for rectifying and filtering the input power. For achieving high performance and low power consumption, the rectifier circuit with low voltage but high output current has become a potential candidate to replace the conventional rectifier circuit. For example, a well-known current-doubler rectifier (CDR) circuit has been proposed for use in high frequency DC/DC converter applications.
Although the current-doubler rectifier circuit is effective for reducing power consumption of the DC/DC converter, there are still some drawbacks. The conventional current-doubler rectifier circuit has separate magnetic components, namely a transformer and at least one inductor. In the transformer of the current-doubler rectifier circuit, a coil is wound around a magnetic core assembly to form as a secondary winding assembly. Since the coil is very thin, its surface area is too small and thus the heat-dissipating efficiency of the transformer is unsatisfied. Since the rectifier circuit needs high output current, a great amount of heat will be generated during operation of the DC/DC converter. The drawback of using the coil as the secondary winding assembly becomes more serious if the output current is increased. Due to the separate arrangement of the transformer and the inductor, a lot of layout area of the system circuit board is occupied by the transformer and the inductor. This configuration results in increased size and cost. Furthermore, since the transformer and the inductor are electrically connected with each other through designed trace patterns, the use of the trace patterns increase power loss of the current-doubler rectifier circuit. Under this circumstance, the converting efficiency of the DC/DC converter is usually insufficient.
Therefore, there is a need of providing an improved transformer so as to obviate the drawbacks encountered from the prior art.